// $Id: Crc.java,v 1.3 2004/02/11 00:51:59 idgay Exp $

/*									tab:4
 * "Copyright (c) 2000-2003 The Regents of the University  of California.  
 * All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without written agreement is
 * hereby granted, provided that the above copyright notice, the following
 * two paragraphs and the author appear in all copies of this software.
 * 
 * IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
 * CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS."
 *
 * Copyright (c) 2002-2003 Intel Corporation
 * All rights reserved.
 *
 * This file is distributed under the terms in the attached INTEL-LICENSE     
 * file. If you do not find these files, copies can be found by writing to
 * Intel Research Berkeley, 2150 Shattuck Avenue, Suite 1300, Berkeley, CA, 
 * 94704.  Attention:  Intel License Inquiry.
 */
package tools.util;

public class Crc {
	public static int calcByte(int crc, int b) {
		crc = crc ^ (int) b << 8;

		for (int i = 0; i < 8; i++) {
			if ((crc & 0x8000) == 0x8000)
				crc = crc << 1 ^ 0x1021;
			else
				crc = crc << 1;
		}

		return crc & 0xffff;
	}

	public static int calc(byte[] packet, int index, int count) {
		int crc = 0;
		int i;

		while (count > 0) {
			crc = calcByte(crc, packet[index++]);
			count--;
		}
		return crc;
	}

	public static int calc(byte[] packet, int count) {
		return calc(packet, 0, count);
	}

	public static void set(byte[] packet) {
		int crc = Crc.calc(packet, packet.length - 2);

		packet[packet.length - 2] = (byte) (crc & 0xFF);
		packet[packet.length - 1] = (byte) ((crc >> 8) & 0xFF);
	}

	public static void main(String[] args) {
		byte[] ia = new byte[args.length];

		for (int i = 0; i < args.length; i++)
			try {
				ia[i] = Integer.decode(args[i]).byteValue();
			} catch (NumberFormatException e) {
			}
		System.out.println(Integer.toHexString(calc(ia, ia.length)));
	}
}
